1. Field of the Invention
The present invention relates to a rubber crawler used in a running section of a vehicle, and in particular to an improved driving rubber projections which project from the inner surface of the crawler.
2. Description of the Related Arts
As a rubber crawler used in a running section of a vehicle, an inner surface-driving type of rubber crawler is known. This is made in such a manner that the inner surface of a rubber crawler will have rubber projections at regular pitches (or intervals) along its longitudinal direction. The rubber projections are engaged with sprockets to transmit driving force or prevent the crawler from coming off from a wheel.
The rubber projections hardly cause any problem when they are properly engaged with the wheel in running. However, when the rubber crawler receives force from its lateral direction or twisting force so that the relative gap between the rubber projections and the sprockets, the wheel and the like is caused, contact and collisions of the rubber projections with the sprockets, the wheel and the like are repeated. This phenomenon is caused so that the gap be canceled and the rubber crawler be restored into the original proper state. During this phenomenon, abrasion and breakage are easily caused in the rubber projection, in particular their both side surfaces.
Thus, proposed is a technique wherein a resin having resistance to abrasion is embedded in the rubber projection in such a manner that the resin will be exposed at both side surfaces of the rubber projection. However, there remains a problem that such abrasion-resistant member is liable to project out or fall away from the rubber projection.
Shearing stress generated in particular when the rubber crawler is rotated is directly transmitted to the body of the rubber crawler through the exposed surface of the abrasion-resistant member, thereby resulting in a problem that cracks are easily caused at the base portion of the rubber projection.
A reinforcing cord such as a steel cord or a bias cord is generally embedded in the rubber elastomer of the rubber crawler along its longitudinal direction. In the case wherein the wheel is rotated while it presses against the inner surface of the rubber crawler when the wheel is driven at a high speed, the rubber portions between lags fall in a crushed state. If this is repeated, the portion in which the reinforcing cord is not embedded (no-cord embedded portion) is bent, especially at the boundary between this portion and the portion in which the reinforcing cord is embedded. As a result, there is caused a problem that cracks are generated at the bent portion, resulting in breakage of the no-cord embedded portion.